US20070223855A1 - Efficient distributed sensor fiber - Google Patents
Efficient distributed sensor fiber Download PDFInfo
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- US20070223855A1 US20070223855A1 US11/535,395 US53539506A US2007223855A1 US 20070223855 A1 US20070223855 A1 US 20070223855A1 US 53539506 A US53539506 A US 53539506A US 2007223855 A1 US2007223855 A1 US 2007223855A1
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- 239000000835 fiber Substances 0.000 title description 3
- 230000003287 optical effect Effects 0.000 claims abstract description 47
- 238000005253 cladding Methods 0.000 claims abstract description 22
- 229910052732 germanium Inorganic materials 0.000 abstract description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 abstract description 4
- 239000000463 material Substances 0.000 abstract description 4
- 238000000034 method Methods 0.000 abstract description 3
- 238000002168 optical frequency-domain reflectometry Methods 0.000 description 5
- 238000000253 optical time-domain reflectometry Methods 0.000 description 5
- 230000001902 propagating effect Effects 0.000 description 5
- 230000005855 radiation Effects 0.000 description 5
- 239000002019 doping agent Substances 0.000 description 4
- 238000001069 Raman spectroscopy Methods 0.000 description 3
- 238000000149 argon plasma sintering Methods 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000004038 photonic crystal Substances 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 230000032258 transport Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
Definitions
- Embodiments of the present invention relate to distributed optical waveguide sensors. More specifically, embodiments of the present invention relate to distributed optical waveguide sensors having optical waveguides with multiple cladding layers.
- Light propagating in a medium can undergo a variety of scattering events, both linear and non-linear.
- Three types of light scattering are Rayleigh, Raman and Brillouin.
- Rayleigh scattering incident light is elastically scattered at the same wavelength.
- Raman scattering incident light is scattered by the vibrations of molecules or optical phonons and undergoes relatively large frequency shifts.
- Brillouin scattering incident light is scattered by acoustic vibrations (phonons) and undergoes relatively small frequency shifts.
- Rayleigh, Raman and Brillouin scattering can be used in distributed optical waveguide sensors to measure a measurand such as temperature or stress over the length of an optical waveguide. Since optical waveguides can be over 30 kilometers long, distributed optical waveguide sensors are suitable for measuring physical parameters over large distances.
- Distributed optical waveguide sensors that use Rayleigh, Raman, or Brillouin scattering are typically based on either Optical Time-Domain Reflectometry (OTDR) or optical frequency-domain reflectometry (OFDR). In either case, high intensity laser light is propagated in the core of an optical waveguide. Light scattering occurs within the waveguide, part of which is captured in the backward propagating modes of the waveguide and can be detected by a receiver. By monitoring one or more variations in the captured light a physical parameter can be determined.
- an optical waveguide with improved scattering efficiency would be useful.
- An optical waveguide that enables improved capture of scattered light would also be useful.
- Embodiments of the present invention generally provide for distributed optical waveguide sensors having optical waveguides with improved scattering efficiency and/or improved light capture.
- Embodiments of the present invention comprise an optical waveguide having multiple cladding layers. Some embodiments have predominantly single-mode cores. Some embodiments have cores that are doped to improve scattering, e.g., highly germanium doped cores. Some embodiments include a first cladding layer and a second cladding layer.
- FIG. 1 is a schematic depiction of a distributed optical waveguide sensor system that is in accord with the principles of the present invention
- FIG. 2 schematically illustrates a section of an optical waveguide that is in accord with the principles of the present invention
- FIG. 3 illustrates the refractive indexes of a double-clad optical waveguide according to one embodiment of the present invention.
- FIG. 4 illustrates the refractive indexes of a double-clad optical waveguide according to another embodiment of the present invention.
- the present invention provides for distributed optical waveguide sensors having optical waveguides with improved scattering efficiency and/or with improved scattered light capture.
- a distributed optical waveguide that is in accord with the principles of the present invention has multiple cladding layers. In some embodiments a predominantly single-mode core, possibly highly germanium doped, provides improved scattering efficiency.
- the multiple cladding layers provide for a multiple mode optical waveguide for improved light capture. It should be understood that the principles of the present invention will boost signal levels for systems using either optical time domain reflectometry (OTDR) or optical frequency domain reflectometry (OFDR).
- OTDR optical time domain reflectometry
- OFDR optical frequency domain reflectometry
- FIG. 1 schematically depicts a distributed optical waveguide sensor system 100 that is in accord with the principles of the present invention.
- the sensor system 100 includes a distributed optical waveguide 102 .
- That optical waveguide which includes a core and multiple cladding layers, is discussed in more detail subsequently.
- the sensor system 100 includes a transmitter 104 and a receiver 106 that is suitable for use with optical time domain or optical frequency domain reflectometry. It is within the scope of the present invention that receiver 106 may comprise any number of individual components necessary to produce or enhance the performance of the invention as described herein.
- Such components include by way of example and not by limitation, a photo detector, a data analyzer, an analogue-to-digital converter, an amplifier, and other similar devices known by those skilled in the art to assist in the reception of light and its meaningful interpretation as set forth herein.
- the transmitter 104 may comprise any number of individual components necessary to produce or enhance the performance of the invention as described herein. Such components include by way of example and not by limitation, a laser, a modulator, a controller, and other similar devices known by those skilled in the art to assist in the generation and transmission of light energy as set forth herein.
- the transmitter 104 and receiver 106 may be in communication (optically or electrically) as necessary for their operation.
- FIG. 2 schematically illustrates a section of the optical waveguide 102 .
- the optical waveguide 102 can be very long, with lengths of 1-30 kilometers being fairly common.
- the optical waveguide 102 is comprised of a core 202 , an inner cladding layer 204 , and an outer cladding layer 206 .
- the core 202 is thin, has a high index of refraction (see FIGS. 3 and 4 ), and often only supports a single transverse optical mode, although multiple modes may also be supported.
- the laser light 210 from the laser source/transmitter 104 travels down the optical waveguide 102 , the laser light 210 is scattered 212 by the waveguide material.
- the interaction 212 of the laser light 210 and the waveguide material produces Rayleigh scattering the incident light is elastically scattered at the same wavelength. If the interaction 212 is with an optical phonon the laser light 210 is Raman scattered with relatively large frequency shifts. If the interaction 212 is with an acoustic vibration (phonons) the laser light 210 is Brillouin scattered with relatively small frequency shifts. In any event, a portion of the scattered laser light 210 having suitable overlap with respect to the propagating modes of the waveguide formed by the core 202 , the inner cladding layer 204 and the outer cladding layer 206 will be recaptured by the optical waveguide 102 .
- the inner cladding 204 and outer cladding 206 form a multi-mode waveguide that efficiently transports the recaptured scattered light (along with the light recaptured by the core propagating modes) to the receiver 106 . That light is collected and processed to determine a physical parameter of interest using known techniques.
- a highly multimode waveguide having a large capture cross-section greatly improves the capture of the scattered light. While the optical waveguide 102 is shown with two cladding layers, in some applications more than two claddings may be used.
- distributed optical waveguides 102 operate by light scattering within the core 202 , it is beneficial to produce as much scattering as possible.
- the pump radiation 210 should be confined in a mode(s) with a small cross-section(s). This produces a high energy density, which increases the scattering efficiency of the non-linear Raman and Brillouin scattering processes.
- a single, well-confined core mode will generally produce the lowest attenuation and dispersion of the propagating laser light 210 .
- a well-confined core mode is particularly useful.
- Core dopants and dopant concentrations such as highly doping the core 202 with germanium, or other dopants as is known, including rare-earth dopants, can increase scattering.
- FIG. 3 illustrates a refractive index profile of a first embodiment optical waveguide
- FIG. 4 illustrates a refractive index profile of a second embodiment optical waveguide.
- distance is shown on the X-axis ( 300 and 400 ) and the refractive index is shown on the Y-axis ( 302 and 402 ).
- the maximum refractive index is in the core 202 , shown as peaks 304 and 404 , while the minimum refractive indexes, shown as lines 306 and 406 , are in the outer cladding layer 206 .
- FIG. 3 illustrates a refractive index profile of a first embodiment optical waveguide
- FIG. 4 illustrates a refractive index profile of a second embodiment optical waveguide.
- distance is shown on the X-axis ( 300 and 400 ) and the refractive index is shown on the Y-axis ( 302 and 402 ).
- the maximum refractive index is in the core 202 , shown as peaks 304 and 404
- the refractive index 308 of the inner cladding layer 204 is constant.
- the embodiment shown in FIG. 3 uses a step index.
- the refractive index 408 of the inner cladding layer changes with radial distance. This can produce a better optical waveguide 102 in some applications.
- waveguides such as fibers with multiple rings of different refractive index or asymmetric transverse sections, waveguides of different or multiple materials (e.g. glasses, liquids, gasses), planar waveguides, so-called ‘holey-fibers’ or photonic crystal structures could all be designed to have the properties described in this invention.
- a wave-guide portion enhances nonlinear scattering through properties such as tight mode confinement, low loss and doping, and a waveguide portion enhances capture of the scattered light through properties such as large modal overlap with the scattered light and high number of guided modes.
- the core of the waveguide structure does not necessarily have to be concentric to the waveguide structure and may be positioned to optimize the recapture of scattered radiation.
- the waveguide structure may even consist of multiple cores, one or more of which guide the pump radiation and one or more of which recapture the scattered radiation in accordance with the principles already outlined.
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- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
A method and apparatus for improving the sensing of a physical parameter using a distributed optical waveguide and scattering. The optical waveguides have improved scattering efficiency and/or improved light capturing capability provided by multi-cladding layers and a tightly confining core waveguide. The core can be highly doped with a material such as germanium to improve scattering. The cladding layers provide a multi-mode waveguide for capturing scattered light. Such optical waveguides are useful in systems that rely on Rayleigh, Raman and Brillouin scattering.
Description
- This application is a continuation of co-pending U.S. patent application Ser. No. 10/862,004, filed Jun. 4, 2004, herein incorporated by reference.
- 1. Field of the Invention
- Embodiments of the present invention relate to distributed optical waveguide sensors. More specifically, embodiments of the present invention relate to distributed optical waveguide sensors having optical waveguides with multiple cladding layers.
- 2. Description of the Related Art
- Light propagating in a medium can undergo a variety of scattering events, both linear and non-linear. Three types of light scattering are Rayleigh, Raman and Brillouin. In Rayleigh scattering, incident light is elastically scattered at the same wavelength. In Raman scattering, incident light is scattered by the vibrations of molecules or optical phonons and undergoes relatively large frequency shifts. In Brillouin scattering, incident light is scattered by acoustic vibrations (phonons) and undergoes relatively small frequency shifts.
- Rayleigh, Raman and Brillouin scattering can be used in distributed optical waveguide sensors to measure a measurand such as temperature or stress over the length of an optical waveguide. Since optical waveguides can be over 30 kilometers long, distributed optical waveguide sensors are suitable for measuring physical parameters over large distances. Distributed optical waveguide sensors that use Rayleigh, Raman, or Brillouin scattering are typically based on either Optical Time-Domain Reflectometry (OTDR) or optical frequency-domain reflectometry (OFDR). In either case, high intensity laser light is propagated in the core of an optical waveguide. Light scattering occurs within the waveguide, part of which is captured in the backward propagating modes of the waveguide and can be detected by a receiver. By monitoring one or more variations in the captured light a physical parameter can be determined.
- While useful, distributed optical waveguide sensors based on scattering have problems because scattering produces signals that are much weaker than the light that created them. In optical waveguides, the originating light, referred to as pump radiation, produces a relatively small amount of scattered light, only a portion of which is captured. Because the captured light is weak, a significant integration time is required to produce measurements with suitable resolution and accuracy.
- Therefore, an optical waveguide with improved scattering efficiency would be useful. An optical waveguide that enables improved capture of scattered light would also be useful.
- Embodiments of the present invention generally provide for distributed optical waveguide sensors having optical waveguides with improved scattering efficiency and/or improved light capture.
- Embodiments of the present invention comprise an optical waveguide having multiple cladding layers. Some embodiments have predominantly single-mode cores. Some embodiments have cores that are doped to improve scattering, e.g., highly germanium doped cores. Some embodiments include a first cladding layer and a second cladding layer.
- So that the present invention can be understood in detail, a particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
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FIG. 1 is a schematic depiction of a distributed optical waveguide sensor system that is in accord with the principles of the present invention; -
FIG. 2 schematically illustrates a section of an optical waveguide that is in accord with the principles of the present invention; -
FIG. 3 illustrates the refractive indexes of a double-clad optical waveguide according to one embodiment of the present invention; and -
FIG. 4 illustrates the refractive indexes of a double-clad optical waveguide according to another embodiment of the present invention. - The present invention provides for distributed optical waveguide sensors having optical waveguides with improved scattering efficiency and/or with improved scattered light capture. A distributed optical waveguide that is in accord with the principles of the present invention has multiple cladding layers. In some embodiments a predominantly single-mode core, possibly highly germanium doped, provides improved scattering efficiency. The multiple cladding layers provide for a multiple mode optical waveguide for improved light capture. It should be understood that the principles of the present invention will boost signal levels for systems using either optical time domain reflectometry (OTDR) or optical frequency domain reflectometry (OFDR).
-
FIG. 1 schematically depicts a distributed opticalwaveguide sensor system 100 that is in accord with the principles of the present invention. As shown, thesensor system 100 includes a distributedoptical waveguide 102. That optical waveguide, which includes a core and multiple cladding layers, is discussed in more detail subsequently. Thesensor system 100 includes atransmitter 104 and areceiver 106 that is suitable for use with optical time domain or optical frequency domain reflectometry. It is within the scope of the present invention thatreceiver 106 may comprise any number of individual components necessary to produce or enhance the performance of the invention as described herein. Such components include by way of example and not by limitation, a photo detector, a data analyzer, an analogue-to-digital converter, an amplifier, and other similar devices known by those skilled in the art to assist in the reception of light and its meaningful interpretation as set forth herein. Similarly, thetransmitter 104 may comprise any number of individual components necessary to produce or enhance the performance of the invention as described herein. Such components include by way of example and not by limitation, a laser, a modulator, a controller, and other similar devices known by those skilled in the art to assist in the generation and transmission of light energy as set forth herein. In addition, thetransmitter 104 andreceiver 106 may be in communication (optically or electrically) as necessary for their operation. -
FIG. 2 schematically illustrates a section of theoptical waveguide 102. It should be understood that theoptical waveguide 102 can be very long, with lengths of 1-30 kilometers being fairly common. As shown, theoptical waveguide 102 is comprised of acore 202, aninner cladding layer 204, and anouter cladding layer 206. Thecore 202 is thin, has a high index of refraction (seeFIGS. 3 and 4 ), and often only supports a single transverse optical mode, although multiple modes may also be supported. Aslaser light 210 from the laser source/transmitter 104 travels down theoptical waveguide 102, thelaser light 210 is scattered 212 by the waveguide material. If theinteraction 212 of thelaser light 210 and the waveguide material produces Rayleigh scattering the incident light is elastically scattered at the same wavelength. If theinteraction 212 is with an optical phonon thelaser light 210 is Raman scattered with relatively large frequency shifts. If theinteraction 212 is with an acoustic vibration (phonons) thelaser light 210 is Brillouin scattered with relatively small frequency shifts. In any event, a portion of thescattered laser light 210 having suitable overlap with respect to the propagating modes of the waveguide formed by thecore 202, theinner cladding layer 204 and theouter cladding layer 206 will be recaptured by theoptical waveguide 102. - The
inner cladding 204 andouter cladding 206 form a multi-mode waveguide that efficiently transports the recaptured scattered light (along with the light recaptured by the core propagating modes) to thereceiver 106. That light is collected and processed to determine a physical parameter of interest using known techniques. A highly multimode waveguide having a large capture cross-section greatly improves the capture of the scattered light. While theoptical waveguide 102 is shown with two cladding layers, in some applications more than two claddings may be used. - Since distributed
optical waveguides 102 operate by light scattering within thecore 202, it is beneficial to produce as much scattering as possible. To that end, thepump radiation 210 should be confined in a mode(s) with a small cross-section(s). This produces a high energy density, which increases the scattering efficiency of the non-linear Raman and Brillouin scattering processes. Additionally, a single, well-confined core mode will generally produce the lowest attenuation and dispersion of the propagatinglaser light 210. As the length of a distributedoptical waveguide 102 increases a well-confined core mode is particularly useful. Core dopants and dopant concentrations, such as highly doping thecore 202 with germanium, or other dopants as is known, including rare-earth dopants, can increase scattering. - The refractive indexes of the
optical waveguide 102 can be adjusted to improve performance.FIG. 3 illustrates a refractive index profile of a first embodiment optical waveguide, whileFIG. 4 illustrates a refractive index profile of a second embodiment optical waveguide. In both figures, distance is shown on the X-axis (300 and 400) and the refractive index is shown on the Y-axis (302 and 402). The maximum refractive index is in thecore 202, shown aspeaks lines outer cladding layer 206. In the embodiment shown inFIG. 3 , therefractive index 308 of theinner cladding layer 204 is constant. Thus, the embodiment shown inFIG. 3 uses a step index. However, in the embodiment shown inFIG. 4 , therefractive index 408 of the inner cladding layer changes with radial distance. This can produce a betteroptical waveguide 102 in some applications. - More complex waveguide structures such as fibers with multiple rings of different refractive index or asymmetric transverse sections, waveguides of different or multiple materials (e.g. glasses, liquids, gasses), planar waveguides, so-called ‘holey-fibers’ or photonic crystal structures could all be designed to have the properties described in this invention. A wave-guide portion enhances nonlinear scattering through properties such as tight mode confinement, low loss and doping, and a waveguide portion enhances capture of the scattered light through properties such as large modal overlap with the scattered light and high number of guided modes.
- The core of the waveguide structure does not necessarily have to be concentric to the waveguide structure and may be positioned to optimize the recapture of scattered radiation. The waveguide structure may even consist of multiple cores, one or more of which guide the pump radiation and one or more of which recapture the scattered radiation in accordance with the principles already outlined.
- While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (1)
1. A distributed optical waveguide sensor apparatus, comprising:
an optical waveguide having a core and a cladding;
a light source for injecting light into said core, wherein said cladding captures and guides light scattered from said core;
a receiver for converting guided, scattered light from said waveguide into electrical signals; and
an analyzer for determining a physical parameter of interest from said electrical signals.
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US11/535,395 US20070223855A1 (en) | 2004-06-04 | 2006-09-26 | Efficient distributed sensor fiber |
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US10/862,004 US7113659B2 (en) | 2004-06-04 | 2004-06-04 | Efficient distributed sensor fiber |
US11/535,395 US20070223855A1 (en) | 2004-06-04 | 2006-09-26 | Efficient distributed sensor fiber |
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US10/862,004 Continuation US7113659B2 (en) | 2004-06-04 | 2004-06-04 | Efficient distributed sensor fiber |
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CN105758622B (en) * | 2016-03-24 | 2017-08-11 | 中国人民解放军国防科学技术大学 | The measuring method of double-clad optical fiber laser cladding light ratio |
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Also Published As
Publication number | Publication date |
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US20050271317A1 (en) | 2005-12-08 |
GB2414795A (en) | 2005-12-07 |
CA2509129C (en) | 2010-03-23 |
US7113659B2 (en) | 2006-09-26 |
GB0511253D0 (en) | 2005-07-06 |
GB2414795B (en) | 2009-03-18 |
CA2509129A1 (en) | 2005-12-04 |
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